The present invention relates to film developing and fixing apparatus particularly adapted for use in connection with high speed, high volume duplicators for making one or more copies of a microfiche master.
In the commonly owned, co-pending U.S. patent application, Ser. No. 504,490, filed Aug. 29, 1974 for FILM DUPLICATOR now U.S. Pat. No. 3,958,142, the disclosure of which is incorporated herein by reference, a high volume, high speed and very economical microfiche duplicator is described and claimed. Generally speaking, that duplicator provides that a master fiche be positioned at a transfer station and that copy film be incremently advanced past the transfer station for "contact printing". After the copy film has been contact printed it is severed from a supply of copy film and placed on a conveyor system which transports the exposed copy film to a film developer where the film is heated, to cooling means for reducing the film temperature, and thereafter past a re-exposure or fixing station where the developed film is again subjected to light to permanently fix the images on the film.
The duplicator disclosed in the referenced U.S. patent employs a conventional film processor for developing and fixing the film. Transport belts advance the exposed film sections through the processor and at the developing and the fixing stations the film movement is arrested for the required length of time to heat and thereby develop the exposed emulsion and to fix the images thereon, respectively. The cooling was accomplished by intimately biasing the film sections into contact with a relatively large diameter cooling drum.
Generally speaking, such prior art processors are disadvantageous in that they require intermittent motion, that is a stop and go conveyor. This requires relatively complicated controls which render the processor expensive. Such intermittent motion is necessary since the emulsion becomes soft and pliable when heated to the developing temperature of about 200.degree.-300.degree. F. When the substance is soft it cannot move relative to stationary components of the film processor because such relative movement can result in surface deformation and damage and a resulting useless film copy.
This problem is particularly severe when belt conveyors are used because they must grasp and/or bias the film against a mating belt, a drum or the like, and since the freshly developed film remains relatively soft. Numerous attempts have been made to overcome this problem, including the use of large cooling drums against which the film is biased after it leaves the developing station, where a drum rotates at the same speed with which the transport belt moves. Although such a construction can prevent relative movements and surface damage therefrom, to achieve a satisfactory cooling rate relatively high contact pressures between the film and the cooling drums are required. These contact pressures are obtained by firmly biasing the transport belt against the drum surface. This biasing pressure and slight surface irregularities in the drum and/or the belt can be sufficient to cause surface indentations which are impressed on the film and which can distort the magnified image to an extent which can make it difficult or impossible to read on a conventional microfiche reader.
In summary, it can be stated that prior art heat sensitive film processors were inefficient in use, relatively expensive to construct and maintain, and had a tendency to cause damage to the fiche. For high quality microfiche records such damage is normally unacceptable. As a compromise the processors were operated at relatively low rates or they required relatively long travel paths for the film to give the film the necessary stay-time within the processors to accomplish all developing-fixing steps. Thus, prior art processors rendered prior art film duplicators and the like relatively expensive and bulky.